Rapid photo-processing developer



United States Patent Malon H. Dickerson, Memphis, Tenn., assignor to the United States of America as representedby the Secretary of the Air Force No Drawing. Application August 6, 1957 Serial No. 676,692

2 Claims. (Cl. 96-66) The present invention relatesgenerally to photographic developing baths and, as illustrated herein, relates more particularly to high speed developers capable of producing fine grain.

Conventional developers require an immersion period in the developer bath of 5 to minutes depending upon the type of developer bath used. Generally, the developer requiring a long period of immersion in the developer bath produces a fine grain While the faster developers requiring shorter periods of immersion do not produce negatives having a grain comparable to those produced by the slow or so-called fine-grain developers.

Conventional high energy type developers are of very high alkalinity, in the order of pH 11 or 12. This high level of alkalinity is the result of the use of sodium hydroxide as other highly ionizing alkaline reagents. The present developer forming the subject matter of the present invention is definitely of the high energy"'type since it accomplishes the work of a high energy developer bath but it does this at approximately the pH level of the conventional fine grain developer pH 8 or a moderate pH of 9.5. Thus the advantages of both the fine grain developer and the high energy developer are combined in a single formula. The difference in alkalinity between a pH 8 and a pH 11 solution is very great and is of great importance since a pH 11 solution is 1000 times more alkaline than a pH 8 solution and therefore has a great enhanced opportunity for softening the gelatin of a photographic emulsion. Such softening would permit graininess or lumping to occur in the emulsion. Likewise, pH 9.5 is relatively low in alkalinity as compared to high energy developers which operate at pH 12 or higher. The difierence in alkalinity between pH 8 and pH 9.5 is one of a factor of ten or less.

The high energy characteristics obtainable at these relatively low pH levels (8 to 9.5) is occasioned by the synergistic effect of the combination of amidol at a low concentration and pyrogallol at a relatively high concentration. Neither of these developing agents used alone in the formula would be satisfactory but when used together in the formulations disclosed herein they form a very satisfactory combination.

The developer baths compounded according to the teachings of the present invention are of the high energy type and require very short processing or immersion periodsto effect full development of normally exposed black and white negative materials and produce grain characteristics comparable to those obtained by the use of conventional fine grain developers.

-The result of development in the pyro-amidol type developers for 30 to 60 seconds at temperatures up to 90 F. yields high gamma values and broad coverage high resolving power values. At the higher temperatures, 80 to 90 F., increases in emulsion speeds are obtained with prehardened Aero Super XX (type 86) aerial film materials. With such materials, which have received normal exposure, the effective emulsion speed when developed in baths commonly used for this purpose is in the order of 2,877, c Pat en'ted' Mar.

to Weston speed rating. However, by the use of pyro-amidol type developers, this speed rating may be increased to 325 for an immersion time of only 30 seconds at 90 F. Higher gammas may be achieved by longer immersion times while maintaining the same speed rating. The resolving power measurement, when using the developer compounded by the use of the present invention, indicate values up to 63 lines per millimeter when Aero Super XX film is developed for 60 seconds.

Conventional developer bath formulae ofier, with-the identical exposure and processing times that are suggested herein, very low resolving power and great loss of. em nlsion speed. That is to say, shouldthe same films be exposed for processing in the present formula at 30 to 60 seconds immersion time, a full scale image with high resolving power is obtained but if the same films were given identical exposures and processed for 30 to '60 seconds in high energy developers, the resolving power might be in the order of 10 lines per millimeter and with a very low contrast image.

The pyro-amidol developer baths, compounded according to the present invention, provide negatives having highly desirable properties which are not normally obtainable by the use of high energy developers. The fine grain characteristics obtainable by the use of the developer bath compounded according to the present invention are comparable to the quality obtainable by the use of so-called low energy, fine grain developers. Additionally, high gamma values and high resolving power values are obtainable at minimum immersion or processing periods without the sacrifice of any of the desirable qualities of the conventional fine grain negative referred to above.

It is possible to obtain a dual image with pyro-amidol developers. In other words, it is possible not only to obtain metallic silver images but also silver and dyeimages. The dye component of this dual image is minus blue and, therefore, contributes to actual printing density since most photographic papers are exposed only by the blue components of white light. The amount of yellow dye image which is formed in-situ with the silver image may be controlled by the amount of sulfite used in the composition of the developer bath. At low sulfite concentrations, in the order of 0.1 mole per liter, the yellow component may comprise as much as 30% of the over-all printing density of the negative. At sulfite concentrations of 0.30 mole per liter, the yellow component of the dual image is about 5% of the over-all printing density of the negative image. At concentrations in excess of 0.40 mole per liter, the yellow dye component is negligible or nonexistent.

The preferred compositions of rapid photo-processing developers prepared with pyrogallol combined with amidol as the developing agents for the development of conventional black and white negative film materials contain the following ingredients:

(a) A compound capable of producing upon solution in water, the 80;, ion, at concentrations of 0.1 to 0.4 mole per liter.

(1:) Pyrogallol (1,2,3-trihydroxybenzene) at concentrations at or in excess of 0.1 mole per liter.

(0) Amidol (2,4-diaminophenol dihydrochloride) at concentrations of 0.01 to 0.15 mole per liter.

(d) A compound capable of producing, in water solution, the OH ion at concentrations sufficient to maintainalkalinity throughout the useful working life of the bath. (2) A compound capable of anti-fogging action, such as the bromide of an alkali metal, at concentrations of 0.02 to 0.10 mole per liter.

Two examples of this type of developer follow: I is a dual-image developer which gives a yellow component of about 30% of the over-all printing density; II is a dual-v I II Components 5 Demineralized water 900 900 Sodium su1fite 12. 6 37.8 Pyrogallol 25. 2 25. 2 Amidol 2. 0 2 0 Sodium Metaborate g 30.0 10 Sodium Carbonate (Mono) g 4-9. 6 Potassium bromide g 3. 0 3. 0 Demineralized water to make .liter. 1 1

These devolper formulae are merely representative of this general type of rapid photo-processing developer and are indicated for development of all black and White roll and sheet film materials, including aerial, amateur and sports films.

Having thus described my invention, What I claim as new and desire to secure by Letters Patent of the United 20 States is:

1. A photographic developer comprising:

1 liter of water 37.8 g. of sodium sulfite 25.2 g. of pyrogallol 2.0 g. of amidol 49.6 g. of sodium carbonate (mono) 3.0 g. of potassium bromide 2. A photographic developer comprising:

1 liter of Water 12.6 to 37.8 g. of sodium sulfite 25.2 g. of pyrogallol 2.0 g. of amidol 30.0 g. of sodium metaborate 3.0 g. of potassium bromide References Cited in the file of this patent PSA Journal (Photo. Sci. Tech.), 1951, 17B: 76. Comm. 1393 (pp. 76-79). (Copy in Div. 60.) 

1. A PHOOTGRAPHIC DEVELOPER COMPRISING: 